The Kyoto Protocol to the United Nations Framework Convention on Climate Change that regulates emissions of greenhouse gas such as carbon dioxide, methane, dinitrogen monoxide, alternative fluorocarbon and the like took effect, and the emission of the greenhouse gas is currently restricted. Therefore, it is an important issue to develop waste heat electric power generation using unused energy that suppresses greenhouse gas emissions. Today, waste heat generated in steel, petroleum, chemical, cement, paper and pulp, ceramic engineering, biomass and various other industries, middle-to-low-temperature waste heat of gas discharged from gas turbines, engines and the like, and heat of waste hot water are not considered to be fully utilized.
In general, an organic rankine cycle (ORC) using an organic compound as a working medium is a closed rankine cycle that does not discharge the working medium outside. An organic rankine cycle device includes an evaporator that evaporates the working medium, a power generator, an expansion device, a condenser, a recirculation pump, and the like. In the rankine cycle, the working fluid passes four steps, namely, adiabatic compression in the pump, isobaric heating (evaporation), adiabatic expansion, and isobaric cooling (condensation) while circulating in the device. The working medium performs heat exchange with an external heat source in the step of isobaric heating, and the evaporated working medium is transferred to the expansion device. The working medium is subjected to adiabatic expansion to provide energy (work) to the outside, and the energy is extracted as electric energy or the like.
Conventionally, water has been practically used as a working medium for many years (see, for example, U.S. Pat. No. 3,393,515). However, water has a high freezing point of 0° C. and a large vapor specific volume. Therefore, when a heat source having a relatively low use temperature range (lower than or equal to about 200° C.) is used, water has drawbacks that the rankine cycle facilities need to be large and that the cycle efficiency is low.
In such a background, various studies have been made on an organic rankine cycle (ORC) as a technology for using low-temperature waste heat. The organic rankine cycle uses an organic compound having a boiling point lower than that of water as a working fluid. A technology of using an organic fluorine compound, among various organic compounds studied, has been proposed.
Japanese Laid-Open Patent Publication No. Hei 2-272086 discloses hydrogen-containing halogenated saturated hydrocarbons having a carbon number of 3, such as 1,1,1,3,3-pentafluoropropane and the like as a working fluid for an organic rankine cycle.
Japanese Laid-Open Patent Publication No. 2007-6684 discloses an organic rankine cycle device that uses 2,2-dichloro-1,1,1-trifluoropropane or 1,1,1,3,3-pentafluoropropane as a working fluid.
Japanese PCT National Phase Laid-Open Patent Publication No. 2012-511087 discloses an organic rankine cycle device that uses fluoroolefins such as 1-chloro-3,3,3-trifluoropropene, monochlorononafluoropentene and the like as a working fluid.
Japanese PCT National Phase Laid-Open Patent Publication No. 2013-500374 discloses an organic rankine cycle system that uses hyodrofluoroolefins having a carbon number of 4, such as 1,1,1,4,4,4-hexafluoro-2-butene and the like as a working fluid.